Convective heat transfer correlations for low-profile spherical cavities with planar bottom surfaces (1415-RP)

Abstract

Domed cavities are found in many building applications, such as conventional skylights and tubular daylighting devices. Heat transfer through domed cavities is thus an important parameter for evaluating the energy performance rating of such skylight systems and in calculating the heating and cooling loads of buildings. Although there have been many studies on the convective heat transfer in related geometries, there is a limited information on natural convective heat transfer in domed cavities with planar inner surfaces. In a previous study, numerical modeling was conducted on natural laminar convective heat transfer in horizontal high-profile domed cavities with planar inner surfaces. In this article, the previous study is extended to investigate the natural convective heat transfer in horizontal low-profile spherical cavities with planar inner surfaces. The bounding surfaces are subject to uniform temperature conditions. The numerical model is based on the finite-element method. The results show that for different boundary temperature conditions, the airflow in the cavities is mono-cellular and reaches steady-state conditions for both cold and hot weather conditions. The numerical results are used to develop practical correlations for the Nusselt number in terms of Rayleigh number.